Polyurethane polishing pad

ABSTRACT

The invention provides a polishing pad suitable for planarizing semiconductor, optical and magnetic substrates. The polishing pad includes a cast polyurethane polymeric material formed from a prepolymer reaction of a polypropylene glycol and a toluene diisocyanate to form an isocyanate-terminated reaction product. The toluene diisocyanate has less than 5 weight percent aliphatic isocyanate; and the isocyanate-terminated reaction product having 5.55 to 5.85 weight percent unreacted NCO. The isocyanate-terminated reaction product being cured with a 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curative agent. The non-porous cured product having a tan delta of 0.04 to 0.10, a Young&#39;s modulus of 140 to 240 MPa and a Shore D hardness of 44 to 56.

BACKGROUND

This specification relates to polishing pads useful for polishing andplanarizing substrates and particularly to planarizing polishing padsproducing low defect levels.

Polyurethane polishing pads are the primary pad-type for a variety ofdemanding precision polishing applications. These polyurethane polishingpads are effective for polishing silicon wafers, patterned wafers, flatpanel displays and magnetic storage disks. In particular, polyurethanepolishing pads provide the mechanical integrity and chemical resistancefor most polishing operations used to fabricate integrated circuits. Forexample, polyurethane polishing pads have high strength for resistingtearing; abrasion resistance for avoiding wear problems duringpolishing; and stability for resisting attack by strong acidic andstrong caustic polishing solutions.

The production of semiconductors typically involves several chemicalmechanical planarization (CMP) processes. In each CMP process, apolishing pad in combination with a polishing solution, such as anabrasive-containing polishing slurry or an abrasive-free reactiveliquid, removes excess material in a manner that planarizes or maintainsflatness for receipt of a subsequent layer. The stacking of these layerscombines in a manner that forms an integrated circuit. The fabricationof these semiconductor devices continues to become more complex due torequirements for devices with higher operating speeds, lower leakagecurrents and reduced power consumption. In terms of device architecture,this translates to finer feature geometries and increased metallizationlevels. These increasingly stringent device design requirements aredriving the adoption of copper metallization in conjunction with newdielectric materials having lower dielectric constants. The diminishedphysical properties, frequently associated with low k and ultra-low kmaterials, in combination with the devices' increased complexity haveled to greater demands on CMP consumables, such as polishing pads andpolishing solutions.

In particular, low k and ultra-low k dielectrics tend to have lowermechanical strength and poorer adhesion in comparison to conventionaldielectrics, rendering planarization more difficult. In addition, asintegrated circuits' feature sizes decrease, CMP-induced defectivity,such as, scratching becomes a greater issue. Furthermore, integratedcircuits' decreasing film thickness requires improvements in defectivitywhile simultaneously providing acceptable topography to a wafersubstrate—these topography requirements demand increasingly stringentplanarity, dishing and erosion specifications.

Casting polyurethane into cakes and cutting the cakes into several thinpolishing pads has proven to be an effective method for manufacturingpolishing pads with consistent reproducible polishing properties. M. J.Kulp, in U.S. Pat. No. 7,414,080, discloses the use of low-free toluenediisocyanate-based polishing pads to improve product uniformity.Unfortunately, polyurethane pads produced from these formulations lackthe planarization and copper dishing properties necessary for the mostdemanding low defect polishing applications.

STATEMENT OF INVENTION

An aspect of the invention provides a polishing pad suitable forplanarizing at least one of semiconductor, optical and magneticsubstrates, the polishing pad comprising a cast polyurethane polymericmaterial formed from a prepolymer reaction of a polypropylene glycol anda toluene diisocyanate to form an isocyanate-terminated reactionproduct, the toluene diisocyanate having less than 5 weight percentaliphatic isocyanate and the isocyanate-terminated reaction producthaving 5.55 to 5.85 weight percent unreacted NCO, theisocyanate-terminated reaction product being cured with a4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curative agent, thecured polymer as measured in a non-porous state having a tan delta of0.04 to 0.10 from 20 and 100° C. with a torsion fixture (ASTM 5279), aYoung's modulus of 140 to 240 MPa at room temperature (ASTM-D412) and aShore D hardness of 44 to 56 at room temperature (ASTM-D2240).

Another aspect of the invention provides a polishing pad suitable forplanarizing at least one of semiconductor, optical and magneticsubstrates, the polishing pad comprising a cast polyurethane polymericmaterial formed from a prepolymer reaction of a polypropylene glycol anda toluene diisocyanate to form an isocyanate-terminated reactionproduct, the toluene diisocyanate having less than 5 weight percentaliphatic isocyanate and the isocyanate-terminated reaction producthaving 5.55 to 5.85 weight percent unreacted NCO, theisocyanate-terminated reaction product being cured with a4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curative agent, thecured polymer as measured in a non-porous state having a tan delta of0.04 to 0.10 from 20 and 100° C. with a torsion fixture (ASTM 5279), aYoung's modulus of 180 to 240 MPa at room temperature (ASTM-D412) and aShore D hardness of 46 to 54 at room temperature (ASTM-D2240).

DESCRIPTION OF THE DRAWING

FIG. 1 represents a plot of Young's modulus versus hardness of padmaterials cured with different curatives.

FIG. 2 is a plot of tan delta from 0 to 100° C. comparing pads polymersprepared with different curatives.

DETAILED DESCRIPTION

The polishing pad is suitable for planarizing at least one ofsemiconductor, optical and magnetic substrates. Most preferably, the padis useful for polishing semiconductor substrates. The polishing padincludes a cast polyurethane polymeric material formed from a prepolymerreaction of a polypropylene glycol, toluene diisocyanate that forms anisocyanate-terminated reaction product. The toluene diisocyanate iscured with a 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curativeagent. The non-porous cured product has a tan delta of 0.04 to 0.10 asmeasured between 20 and 100° C. for consistent polishing behavior up tohigh temperatures. In addition, the non-porous cured product has aYoung's modulus of 140 to 240 MPa. This modulus provides an excellentcombination of planarization, TEOS erosion and copper dishingperformance. Preferably, the non-porous cured product has a Young'smodulus of 180 to 240 MPa. For low defectivity, the non-porous curedproduct has a Shore D hardness of 44 to 56. Most preferably, thenon-porous cured product has a Shore D hardness of 46 to 54.

The polymer is effective for forming non-porous; and porous or filledpolishing pads. For purposes of this specification, filler for polishingpads include solid particles that dislodge or dissolve during polishing,and liquid-filled particles or spheres. For purposes of thisspecification, porosity includes gas-filled particles, gas-filledspheres and voids formed from other means, such as mechanically frothinggas into a viscous system, injecting gas into the polyurethane melt,introducing gas in situ using a chemical reaction with gaseous product,or decreasing pressure to cause dissolved gas to form bubbles. Theporous polishing pads contain a porosity or filler concentration of atleast 0.1 volume percent. This porosity or filler contributes to thepolishing pad's ability to transfer polishing fluids during polishing.Preferably, the polishing pad has a porosity or filler concentration of0.2 to 70 volume percent. Most preferably, the polishing pad has aporosity or filler concentration of 0.25 to 60 volume percent.Optionally, the pores have an average diameter of less than 200 μm.Preferably, the pores or filler particles have a weight average diameterof 10 to 100 μm. Most preferably, the pores or filler particles have aweight average diameter of 15 to 90 μm. The nominal range of expandedhollow-polymeric microspheres' weight average diameters is 15 to 50 μm.

Optionally, the pad is non-porous. Non-porous pads are particularlyuseful for applications requiring excellent pad life and planarization.In particular, non-porous pads having macrogrooves and a roughenedsurface from a diamond conditioner are effective for copper and tungstenapplications. Generally, increasing macrotexture or microtextureincreases the removal rate for the non-porous pads.

Controlling the unreacted NCO concentration is particularly effectivefor controlling the pore uniformity for pores formed directly orindirectly with a filler gas. This is because gases tend to undergothermal expansion at a much greater rate and to a greater extent thansolids and liquids. For example, the method is particularly effectivefor porosity formed by casting hollow microspheres, either pre-expandedor expanded in situ; by using chemical foaming agents; by mechanicallyfrothing in gas; and by use of dissolved gases, such as argon, carbondioxide, helium, nitrogen, and air, or supercritical fluids, such assupercritical carbon dioxide or gases formed in situ as a reactionproduct.

The polymeric material is a polyurethane formed with polypropylene etherglycol [PPG] and 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline)[MCDEA]. For purposes of this specification, “polyurethanes” areproducts derived from difunctional or polyfunctional isocyanates, e.g.polyotherureas, polyesterureas, polyisocyanurates, polyurethanes,polyureas, polyurethaneureas, copolymers thereof and mixtures thereof.An approach for controlling a pad's polishing properties is to alter itschemical composition. In addition, the choice of raw materials andmanufacturing process affects the polymer morphology and the finalproperties of the material used to make polishing pads.

Preferably, urethane production involves the preparation of anisocyanate-terminated urethane prepolymer from a polyfunctional aromaticisocyanate and a prepolymer polyol. For purposes of this specification,the term prepolymer polyol is polypropylene ether glycol [PPG],copolymers thereof and mixtures thereof. Preferably, the polyfunctionalaromatic isocyanate toluene diisocyanate that contains less than 5weight percent aliphatic isocyanate and more preferably, less than 1weight percent aliphatic isocyanate.

Typically, the prepolymer reaction product is reacted or cured with4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) or mixture thereof;such as with other polyamines. For purposes of this specification,polyamines include diamines and other multifunctional amines. Examplesof other curative polyamines include aromatic diamines or polyamines,such as, 4,4′-methylene-bis-o-chloroaniline [MOCA];dimethylthiotoluenediamine; trimethyleneglycol di-p-aminobenzoate;polytetramethyleneoxide di-p-aminobenzoate; polytetramethyleneoxidemono-p-aminobenzoate; polypropyleneoxide di-p-aminobenzoate;polypropyleneoxide mono-p-aminobenzoate;1,2-bis(2-aminophenylthio)ethane; 4,4′-methylene-bis-aniline;diethyltoluenediamine; 5-tert-butyl-2,4- and3-tert-butyl-2,6-toluenediamine; 5-tert-amyl-2,4- and3-tert-amyl-2,6-toluenediamine and chlorotoluenediamine. Preferably, theprepolymer reaction product is reacted or cured with a single4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) curative. Optionally,it is possible to manufacture urethane polymers for polishing pads witha single mixing step that avoids the use of prepolymers.

The polyurethane polymeric material is preferably formed from aprepolymer reaction product of toluene diisocyanate and polypropyleneether glycol with 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline).Preferably, the prepolymer reaction product has a 5.55 to 5.85 weightpercent unreacted NCO. Preferably, the prepolymer has less than 0.1weight percent free TDI monomer and has a more consistent prepolymermolecular weight distribution than conventional prepolymers, and sofacilitate forming polishing pads with excellent polishingcharacteristics. This improved prepolymer molecular weight consistencyand low free isocyanate monomer give an initially lower viscosityprepolymer that tends to gel more rapidly, facilitating viscositycontrol that can further improve porosity distribution and polishing padconsistency. In addition, low molecular weight polyol additives, suchas, diethylene glycol, butanediol and tripropylene glycol facilitatecontrol of the prepolymer reaction product's weight percent unreactedNCO.

In addition to controlling weight percent unreacted NCO, the curativeand prepolymer reaction product preferably has an OH or NH₂ to unreactedNCO stoichiometric ratio of 80 to 120 percent; and most preferably, ithas an OH or NH₂ to unreacted NCO stoichiometric ratio of 100 to 112percent.

If the polishing pad is a polyurethane material, then the polishing padpreferably has a density of 0.5 to 1.25 g/cm³. Most preferably,polyurethane polishing pads have a density of 0.6 to 1.15 g/cm³.

For non-porous pads, typical circular or circular plus radial groovepatterns are effective. Preferably the groove pattern is a an overlay oftwo groove patterns, a first larger pattern for removing debris and asecond smaller channel for increasing removal rate. For example,circular grooves having a depth of 30 mils (0.760 mm), width of 20 mils(0.508 mm) and a pitch of 120 mils (3.05 mm) represents the first largerchannel and second set of three circular grooves having a depth of 15mils (0.381 mm), width of 10 mils (0.254 mm) and a pitch of 30 mils(0.760 mm) provides the smaller channel. This combination of large andsmall channels can contribute toward an effective combination of lowdefectivity, process stability and high rate.

EXAMPLES

Cast polyurethane cakes were prepared by the controlled mixing of (a) anisocyanate terminated prepolymer at 51° C. (or desired temperaturesbased on various formulations) obtained by the reaction of apolyfunctional isocyanate (i.e., toluene diisocyanate) and a polyetherbased polyol (for example, Adiprenee LF750D and others listed in Tablescommercially available from Chemtura Corporation); (b) a curative agentat 116° C. and optionally, (c) a hollow core filler (i.e., Expancel®551DE40d42, 551DE20d60, 461DE20d70, or 920DE80d30 available from AkzoNobel). The ratio of the isocyanate terminated prepolymer and thecurative agent was set such that the stoichiometry, as defined by theratio of active hydrogen groups (i.e., the sum of the —OH groups and—NH₂ groups) in the curative agent to the unreacted isocyanate (NCO)groups in the isocyanate terminated prepolymer, was set according toeach formulation as listed in Tables. The hollow core filler was mixedinto the isocyanate terminated prepolymer prior to the addition of thecurative agent. The isocyanate terminated prepolymer with theincorporated hollow core filler were then mixed together using a highshear mix head. After exiting the mix head, the combination wasdispensed over a period of 5 minutes into a 86.4 cm (34 inch) diametercircular mold to give a total pour thickness of approximately 8 cm (3inches). The dispensed combination was allowed to gel for 15 minutesbefore placing the mold in a curing oven. The mold was then cured in thecuring oven using the following cycle: 30 minutes ramp of the oven setpoint temperature from ambient temperature to 104° C., then hold for15.5 hours with an oven set point temperature of 104° C., and then 2hour ramp of the oven set point temperature from 104° C. down to 21° C.

The cured polyurethane cakes were then removed from the mold and skived(cut using a moving blade) at a temperature of 30 to 80° C. intomultiple polishing layers having an average thickness of 2.0 mm (80mil). Skiving was initiated from the top of each cake.

Example 1

Table 1 includes the formulations for a series of pads manufactured tothe above method with various prepolymers, isocyanate amounts andcuratives.

TABLE 1 Adiprene ® and Vibrathane ® are urethane prepolymer products ofChemtura Corporation all NCO values represent nominal amounts. UnreactedIsocyanate NCO Stoichiometry Formulation Polyol Backbone Prepolymer Wt.% Curative (%) A-1 PTMEG Adiprene LF750D 8.9 MOCA 85 B-1 PTMEG AdipreneLF750D 8.9 MOCA 105 C-1 PTMEG Adiprene LF750D 8.9 MOCA 115 D-1 PTMEG/PPGAdiprene LF750D/ 8.8 MOCA 95 LFG740D E-1 PTMEG/PPG Adiprene LF750D/ 7.3MOCA 97 LFG963A F-1 PPG Vibrathane B628 4.2 MOCA 95 F-2 PPG VibrathaneB628 4.2 MOCA 105 G-1 PTMEG Adiprene LF900A 3.8 MOCA 95 G-2 PTMEGAdiprene LF900A 3.8 MOCA 105 H-1 PTMEG Adiprene LF800A 2.9 MOCA 95 H-2PTMEG Adiprene LF800A 2.9 MOCA 105 I-1 PPG Adiprene LFG963A 5.75 MOCA 90I-2 PPG Adiprene LFG963A 5.75 MOCA 102.5 1 PPG Adiprene LFG963A 5.75MCDEA 102.5 2 PPG Adiprene LFG963A 5.75 MCDEA 110 E-2 PTMEG/PPG AdipreneLF750D/ 7.3 MCDEA 110 LFG963A E-3 PTMEG/PPG Adiprene LF750D/ 7.3 MCDEA110 LFG963A J-1 PPG Adiprene LFG963A/ 8.47 MCDEA 110 H12MDI F-5 PPGVibrathane B628 4.2 MCDEA 85 F-4 PPG Vibrathane B628 4.2 MCDEA 95 G-3PTMEG Adiprene LF900A 3.8 MCDEA 85 G-4 PTMEG Adiprene LF900A 3.8 MCDEA95 H-3 PTMEG Adiprene LF800A 2.9 MCDEA 85 H-4 PTMEG Adiprene LF800A 2.9MCDEA 95 K-1 PTMEG Adiprene LF667 6.67 MCDEA 110 LFG963A is a TDI-PPGprepolymer having a nominal unreacted NCO of 5.75 wt % and a range of5.55 to 5.85 wt %.

Several samples from Table 1 prepared as above were tested for physicalproperties with an initial screen. The test method for Young's modulus(ASTM-D412) specimen geometry was as follows: dumbbell shape with 4.5inch (11.4 cm) in total length, 0.75 inch (0.19 cm) in total width, 1.5inch (3.8 cm) in neck length and 0.25 inch (0.6 cm) in neck width. Thegrip separation was at a rate of 20 inch/min. (50.8 cm/min.). Thehardness measurements were in accordance with ASTM-D2240 to measureShore D hardness using a Shore S1, Model 902 measurement tool with a Dtip. Table 2 below compares hardness and modulus based upon prepolymeras a function of NCO and curative.

TABLE 2 Hardness Formu- Prepolymer Stoichiometry (Shore Modulus lationNCO Wt. % Curative % D) (MPa) A-1 8.9 MOCA 85 67.0 431 B-1 8.9 MOCA 10566.0 380 C-1 8.9 MOCA 115 71.0 503 D-1 8.8 MOCA 95 65.4 372 E-1 7.3 MOCA97 58.0 215 F-1 4.2 MOCA 105 45.5 41.7 F-2 4.2 MOCA 95 34.0 28.0 F-3 4.2MOCA 104 30.6 24.4 G-1 3.8 MOCA 95 40.0 33.9 G-2 3.8 MOCA 105 36.6 28.2H-1 2.9 MOCA 95 29.0 18.9 H-2 2.9 MOCA 105 25.6 17.1 I-1 5.75 MOCA 9050..0 119 1 5.75 MCDEA 102.5 51.5 222 2 5.75 MCDEA 110 48.0 190 E-2 7.3MCDEA 110 56.0 294 E-3 7.3 MCDEA 110 61.0 348 J-1 8.47 MCDEA 110 68.0416 F-4 4.2 MCDEA 95 46.0 45.6 F-5 4.2 MCDEA 85 43.4 41.0 G-4 3.8 MCDEA95 45.0 51.0 G-3 3.8 MCDEA 85 43.8 45.8 H-4 2.9 MCDEA 95 35.0 26.0 H-32.9 MCDEA 85 33.6 25.5

As illustrated in FIG. 1, samples 1 and 2 with 5.75 wt % (5.55 to 5.85wt %) NCO provided an unexpected combination of Shore D hardness andYoung's modulus.

A DMA comparison between samples 1 and I-2 was done in accordance withASTM 5279 at a rate of 10 radians/s and a heating rate of 3° C. perminute using non-porous samples having specimen dimensions of 40 mm×6.5mm×1.27 mm after five days of conditioning at room temperature in 50%humidity chamber using Torsion Rectangular fixture on a RheometricScientific RDA3 DMA tool. As seen from FIG. 2, the MCDEA-curedformulation with 5.75 wt % (5.55 to 5.85 wt %) NCO provided anunexpected flat tan delta in comparison to the MOCA-cured formulation.In particular, this combination provides having a tan delta of 0.04 to0.10 as measured between 20 and 100° C. Polishing with MOCA-cured padshaving an NCO below 5.55 weight percent and above 5.85 weight percentlack the improved combination of planarization and low dishing achievedwith similar MCDEA-cured formulations.

Example 2

Porous formulations of pad samples used in bulk copper polishing testswere modified as illustrated in Table 3.

TABLE 3 EXPANCEL Estimated Unreacted Polymer Microsphere NCOMicrospheres Microsphere Density Formulation Wt. % CurativeStoichiometry % (Diameter) Wt. % (g/cc) 1-A 5.75 MCDEA 102.5 461DE20d701.92 0.070 (20 μm) I-1 5.75 MOCA 90 551DE40d42 1.12 0.042 (40 μm) E-47.3 MOCA 97 551DE20d60 2.06 0.060 (20 μm) L-1 8.8 MOCA 95 551DE20d601.35 0.060 (20 μm)

A polishing defect comparison was then completed between formulation 1Aand comparative formulation E-4. The pads Polishing conditions were withgrooves having a depth of 30 mils (0.760 mm), width of 18 mils (0.457mm) and a pitch of 70 mils (1.778 mm) on an Applied Materials ReflectionLK tool, with a wafer velocity of 87 rpm and a platen velocity of 93 rpmusing in-situ conditioning with a Kinik AD3BG-150855 diamond conditionerusing Planar Solution CSL9044C slurry. Copper blanket wafers wereinspected using KLA-Tencor Surfscan SPITBI with a threshold at 0.07microns and the defect map was output by KLARF v 0.2 for further reviewusing KLA-Tencor eDR5210 Review SEM for defect classification.

Table 4 for FIG. 3. Defect comparison between E-4and 1-A Random MicroStoic Porosity Defect Scratch Formulation Prepolymer Curative (%) (vol.%) (No.) (No.) E-4 LF750D/LFG963A MOCA 97 32 2249 306 1-A LFG963A MCDEA102.5 24 1884 34

These data show that despite the similar modulus, formulation I-Aprovided a low defectivity. In particular, formulation 1-A provided asignificant decrease in microscratches in comparison to theMOCA-containing comparative E-4.

Example 3

The pads of Table 3 were then tested for dishing on an Applied MaterialReflexion LK tool. Tables 5 and 6 below provides dishing at variousdensities after 60 seconds over polishing.

TABLE 5 Stoic Porosity 10 × 10 μm 50 × 50 μm 100 × 100 μm FormulationPrepolyrner Curative (%) (vol. %) (No.) (No.) (No.) E-4 LF750D/LFG963AMOCA 97 32 534 756 850 1-A LFG963A MCDEA 102.5 24 447 484 538 L-1LFG740D MOCA 95 32 585 905 1050

TABLE 6 Stoic Porosity 7 × 3 μm 9 × 1 μm 100 × 1 μm FormulationPrepolymer Curative (%) (vol. %) (No.) (No.) (No.) E-4 LF750D/LFG963AMOCA 97 32 547 780 1406 1-A LFG963A MCDEA 102.5 24 481 605 676 L-1LFG740D MOCA 95 32 540 830 1650

Tables 5 and 6 show the MCDEA pad of the invention having the bestdishing performance at the densities tested. Since pads with low defectsoften have higher dishing, this represents an unexpected feature of theinvention. Additional tests have shown that a stoichiometry of 100 to112 percent provides the best dishing performance and exhibits the besttopography performance.

Example 4

In addition, the non-porous version of the formulation has a particularaffinity to tungsten polishing. Polishing conditions were with grooveshaving a depth of 30 mils (0.760 mm), width of 20 mils (0.508 mm) and apitch of 120 mils (3.05 mm) on an Applied Materials Mirra tool, with awafer velocity of 111 rpm and a platen velocity of 113 rpm using ex-situconditioning with a Saesol AM02BSL8031C1-PM diamond conditioner usingCabot SS2000 tungsten slurry. In particular, it out preformed theindustry standard, IC1010 in a head to head comparison as follows:

TABLE 7 IC1010 Polyurethane Pad Formulation 1 Sheet Data TungstenRemoval Rate 3000 3565 (Å/min.) Range 1000 1171 TEOS Removal Rate(Å/min.) 50 50 Avg. Ra (μm) 5.5 2.7 Pattern data Total Metal Loss (Cu +TEOS 856 810 μm) Clear Time (Seconds) 83 91 Max. Temp (° C.) 58 46

Table 7 shows a significant improvement in tungsten removal rate for theMCDEA formulation of the invention. Furthermore, combining the low TEOSdefectivity of Table 4 with the increased removal tungsten removal rateprovides an excellent polishing combination not achieved withconventional polishing pads.

In summary, the specific combination of 5.55 to 5.85 wt % NCOpolypropylene glycol in combination with a MCDEA curative provides anexcellent combination of planarization, low defects and low copperdishing for copper polishing applications. Furthermore, this formulationpossesses a stable tan delta between 20 and 100° C. for consistentpolishing with minor temperature variations. Finally, the formulationprovides non-porous pads having excellent tungsten removal rate incombination with low TEOS defectivity.

1. A polishing pad suitable for planarizing at least one ofsemiconductor, optical and magnetic substrates, the polishing padcomprising a cast polyurethane polymeric material formed from aprepolymer reaction of a polypropylene glycol and a toluene diisocyanateto form an isocyanate-terminated reaction product, the toluenediisocyanate having less than 5 weight percent aliphatic isocyanate andthe isocyanate-terminated reaction product having 5.55 to 5.85 weightpercent unreacted NCO, the isocyanate-terminated reaction product beingcured with a 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curativeagent, the cured polymer as measured in a non-porous state having a tandelta of 0.04 to 0.10 from 20 and 100° C. with a torsion fixture (ASTM5279), a Young's modulus of 140 to 240 MPa at room temperature(ASTM-D412) and a Shore D hardness of 44 to 56 at room temperature(ASTM-D2240).
 2. The polishing pad of claim 1 wherein the polishing padis non-porous.
 3. The polishing pad of claim 1 wherein theisocyanate-terminated reaction product and the4,4′-methylene-bis(3-chloro-2,6-diethylaniline) has an NH₂ to NCOstoichiometric ratio of 80 to 120 percent.
 4. The polishing pad of claim1 wherein the polishing pad includes pores having an average diameter ofless than 200 μm.
 5. The polishing pad of claim 4 wherein the polishingpad includes polymeric microspheres to form pores.
 6. A polishing padsuitable for planarizing at least one of semiconductor, optical andmagnetic substrates, the polishing pad comprising a cast polyurethanepolymeric material formed from a prepolymer reaction of a polypropyleneglycol and a toluene diisocyanate to form an isocyanate-terminatedreaction product, the toluene diisocyanate having less than 5 weightpercent aliphatic isocyanate and the isocyanate-terminated reactionproduct having 5.55 to 5.85 weight percent unreacted NCO, theisocyanate-terminated reaction product being cured with a4,4′-methylene-bis(3-chloro-2,6-diethylaniline) curative agent, thecured polymer as measured in a non-porous state having a tan delta of0.04 to 0.10 from 20 and 100° C. with a torsion fixture (ASTM 5279), aYoung's modulus of 180 to 240 MPa at room temperature (ASTM-D412) and aShore D hardness of 46 to 54 at room temperature (ASTM-D2240).
 7. Thepolishing pad of claim 6 wherein the polishing pad is non-porous.
 8. Thepolishing pad of claim 6 wherein the isocyanate-terminated reactionproduct and the 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) has anNH₂ to NCO stoichiometric ratio of 100 to 112 percent.
 9. The polishingpad of claim 6 wherein the polishing pad includes pores having anaverage diameter of 5 to 100 μm.
 10. The polishing pad of claim 9wherein the polishing pad includes polymeric microspheres to form thepores.